Artificial leather made of collagen fibers mixed with synthetic fibers and method of making same

ABSTRACT

Manufacturing leather substitutes comprising the steps of preparing dry collagen fibers and synthetic fibers, forming a web of said fibers and apply an adhesive bonding agent thereto to produce a web having fibers in three dimensional pattern.

United States Patent Ladislav Bogdanovlcz Kunovice;

Zdenek Eckmayer, Otrokovlce; Zdenek Hrabal, Otrokovlee; Radlro Krcrna, Brno; Vaclav Mrstina, Brno; Antonin Pavllk, Strellce; Rudolf Vilcek, Oldrlchovlce, all of Czechoslovakia Nov. 10, 1966 Sept. 2 I 197 1 SVI'I, Narodni Podnlk Gottwaldov, Czechoslovakia Nov. 13, 1965 Czechoslovakia Inventors Appl. No. Filed Patented Assignee Priority ARTIFICIAL LEATHER MADE OF COLLAGEN FIBERS MIXED WITH SYNTHETIC FIBERS AND METHOD OF MAKING SAME 8 Claims, No Drawings References Cited UNITED STATES PATENTS Glover Simril Semegen Merriam et a1.

Klevens Young et a1. Satas Klevens... Dodge Van Saun Oace Young et a1. Patsis Great Britain Primary Examiner-John T, Goolkasian Assistant Examiner-Willard E Hoag Allorney- Richard Low 28/723 117/7 117/76 106/155X 264/212X 241/4 161/72 106/155 161/170X 161/50 161/170X 161/170X 161/157X ABSTRACT: Manufacturing leather substitutes comprising the steps of preparing dry collagen fibers and synthetic fibers, forming a web of said fibers and apply an adhesive bonding agent thereto to produce a web having fibers in three dimensional pattern.

ARTIFICIAL LEATHER MADE OF COLLAGEN FIBERS MIXED WITH SYNTHETIC FIBERS AND METHOD OF MAKING SAME This invention relates to leather substitutes and to their manufacture, and particularly to an artificial leather prepared from tannery waste and like collagen-bearing material.

Leather of proper quality for the manufacture of shoe uppers and of leather clothing other than footwear is limited in supply, relatively costly, and of variable quality. The leather substitutes available so far do not combine the desirable properties of natural leather with lower price and greater uniformity in a satisfactory manner.

An object of the invention is the provision of a leather substitute which has all the necessary mechanical properties for use in shoe uppers and in leather clothing, more specifically high resistance to repeated bending (absence of fiexural fatigue), high tear strength and resistance to propagation of tears under stress.

Another object is the provision of a leather substitute which has the permeability to air and water vapor characteristic of the natural product.

Yet another object is the provision of a leather substitute which has the softness, suppleness, hand, and foldability of the grades of leather preferred in good leather clothing.

An additional object is the provision of a leather substitute which can be made from inexpensive raw materials in a simple manner.

With these and other objects in view, as will hereinafter become apparent, this invention in one of its aspects resides in a leather substitute which is basically a nonwoven fabric structure and whose fiber base consists of a major amount of collagen fibers at least 1 centimeter long and of a minor amount of manmade fibers, preferably staple fibers chopped to a length substantially greater than the length of the collagen fibers. The various types of fibers are entangled with each other in a three-dimensional pattern, and are bonded to each other by an adhesive.

The invention, in another aspect, resides in a method of making a leather substitute in which the aforementioned fibers are first mixed with each other, then formed into a web, and tangled while in the web form before they are adhesively bonded to each other by means of an adhesive which has the necessary affinity for collagen fibers. The machines conventionally employed in the making of nonwoven fabrics, battings, or felts may be used for performing the method.

The following examples further illustrate this invention, but it will be understood that the invention is not limited thereto.

EXAMPLE 1 Split from the flesh side of cowhide shoulders was limed in the tannery in the usual manner and washed in running water. It was then cut into pieces about 4 inches square and delimed in a 0.3 percent ammonium sulfate solution at a liquor ratio of 200 percent and a temperature of 25 C. After about four hours, the operation was terminated, and deliming had progressed to about two-thirds in the heavier pieces.

The pieces were then immersed in a solution containing 2 percent of a proteolytic enzyme on the weight of the pelt pieces and a liquor ratio of 200 percent. The enzyme had a strength of 833 casein units and was applied for 24 hours. The bath was then replaced by a fresh enzyme solution of the same composition, the treatment was continued for an additional period of 24 hours, and was followed by washing in running water at 25 C.

The pieces were then pickled for two hours in an aqueous bath containing 7 percent sodium chloride and 1.5 percent sulfuric acid, and were thereafter tanned for 1 hour in a liquor-containing alum to a basicity of 40 Sch. (Schorlemmer), containing 2 percent chromium trioxide on the weight of the pieces, and neutralized by 0.4 percent soda. The tanned material was washed in clean running water for 2 hours.

The collagen fibers were then separated from each other by passing the tanned pieces suspended in 5 times their weight of water through a horizontal disc-type disintegrator, and the fibers were separated from excess water by passing the pulp discharged from the disintegrator between rubber coated rolls. The collected fibers were ultimately dried at room temperature to equilibrium with the ambient air. The collagen fibers obtained had an average length of somewhat more than i centimeter.

Alternating thin layers of the collagen fibers and of polypropylene staple fibers were superimposed on each other. The synthetic fibers had a length of 6 cm. and a denier count of 3.5, and amounted to one-quarter of the collagen fibers. Sections of the laminar fiber stack obtained were passed over an opener for mixing the two types of fibers.

The fiber mixture was fed to a roller card provided with medium-fine card clothing and a crosser lapper which laid the carded fleece to a weight of 200 grams per square meter. The collagen fibers and polypropylene fibers were intimately mixed in the resulting web, and the latter was passed through a needle-punching machine of the type conventionally employed in making felt of synthetic fibers. The barbed needles, moving transversely in and out of the web at a rate of approximately 200 passes per cm. caused three-dimensional fiber entanglement. The fabric gained substantial mechanical strength by this treatment and was then exposed to live saturated steam for five minutes by continuous passage through a shrinking chamber from which it was led through a drying chamber, and then through a solution of a polyurethane bonding agent prepared in the following manner:

15 Moles polypropyleneglycol ether of molecular weight 3000 were heated with 4 moles 2,4-toluene diisocyanate to 7080 C. for three hours with agitation. The prepolymer so obtained was dissolved in 9 kg. dimethylformamide, and a mixture of 5 moles distilled water with 10 kg. dimethylformamide was added. The temperature of the resulting mixture was raised to 1 10 C., and held at that temperature with stirring for about 10 to 15 minutes. It was then cooled, a solution of 0.7 mole diethylamine in 8 kg. dimethylformamide was added, and stirring was continued for 1 hour, whereupon 3 moles 2.4- toluene diisocyanate dissolved in 2 kg. dimethylformamide were added.

The solution ultimately produced contained approximately 20 percent nonvolatile material or binder solids which had free isocyanate groups. The dry fiber material was impregnated with the bonding agent to a pickup of 65 percent, and was then passed through water to precipitate the resin and to remove the excess of dimethylformamide solvent. The thoroughly washed impregnated web was then dried, and its surface was polished. The product obtained had the appearance of natural leather suitable for shoe uppers. It could be embossed to simulate grain or otherwise finished. The following properties were characteristic of several batches of the material prepared under conditions similar to those outline above, but with varying amounts of binder solids.

Thickness l.2-l .4 mm.

Resin content 25-401 Tensile strength 0.6-l.l kg. per mm. Elongation 60-80% Stitch tearing strength 4.5-5.0 kg. per mm. Water absorptivity -l 507:

Water vapor permeability Tear propagation resistance 3-5 mg. per hour per cm. 3.0-4.0 kg. per mm.

EXAMPLE 2 the hair side from the hide pieces, liming was completed by soaking 48 hours in a solution of 3.5 percent calcium hydroxide and 3.5 percent sodium sulfate, whereupon 5 percent sodium hydroxide on the weight of the hide cuttings were added, and soaking was continued for 48 hours. The limed material was then washed in running water for about 2 to 4 hours, and further worked up to produce collagen fibers as described in example 1.

The collagen fibers were mixed with percent Dacron polyester staple fibers of 3.5 denier and 60 mm. length and with 20 percent viscose rayon staple fibers of 3.5 denier and 60 mm. length by layering and opening as described in example 1. The mixture was converted to a web by suspending the fibers in a stream of air and depositing them at random on a traveling screen at a rate of 150 grams per square meter. The web obtained was reinforced by stitch bonding the same with nylon yarn on a machine similar to a warp knitting machine in which binding yarns were passed back and forth through the web by means of latch needles in the form of loops closely similar to the loops of warp knit material.

The reinforced nonwoven fabric was passed through a conventional saturator and impregnated with a polyurethane binder as described in example 1. It was drummed dry in a manner conventional in leather finishing.

The product obtained had the appearance and hand of soft leather, and was suitable for making blouses, coats, and overcoats, also as a lining for fur coats.

EXAMPLE 3 A material suitable for shoe linings, insoles, and slip soles was made from collagen fibers prepared as described in example l which were mixed with percent polyvinyl chloride fibers and made into a web by air deposition to a weight of 400 grams per square meter.

The web was reinforced by stitch bonding with nylon yarn in an amount sufficient to make the nylon content of the stitched material 8 percent. It was passed through a water tank at 90 C. for a dwell time of 60 to 120 seconds for shrinkage, dried, and impregnated with a polyamide bonding agent on a saturator in the manner described in example 1.

The bonding agent or binder was prepared by depolymerizing a polyamide resin in an alcoholic medium with paraformaldehyde at 90 C. Phosphoric acid was then added as a catalyst and the temperature was raised to 140 C. while the reaction mixture was stirred. It was then poured into water, whereby a modified polyamide resin was precipitated. It was washed with water to remove all phosphoric acid, dried, and dissolved in methanol to which 10 percent dioctyl phthalate on the weight of the polyamide was added. The solution was employed as a binder which was applied to the collagen-polyvinyl chloride web and was cured by evaporation of the methanol at a temperature of 90-l00 C. on a conventional padding machine.

Several batches of the leatherlike product obtained had the following characteristic properties:

Thickness l.2-l.4 mm.

Resin content (binder) 30-35% Tensile strength 0.7-l .2 kg. per mm. Elongation 40-701 Stitch tearing strength 4.8-5.2 kg. per mm. Water absorptivity 60- l 00% 2-3 mg. per hour per cm. 3.2-4.3 kg. per mm.

Permeability to water vapor Tear propagation resistance fully. The collagen fibers must not be shorter than 1 centimeter, and it is necessary that the collagen fibers be entangled or interlaced in a three-dimensional pattern with the manmade fibers in the leather substitute which is produced when a web of mixed fibers is adhesively bonded by binders of which only a few preferred examples have been referred to by way of example.

The binders conventionally employed in the making of nonwoven fabrics are applicable at least to some extent to this invention, but preliminary tests are advisable to select a binder of good adhesion to collagen where full mechanical strength is to be achieved. The polyurethane and polyamide binders more specifically described above have been found to yield the strongest leather substitutes among many adhesives tested, but excellent adhesion to collagen fibers is also obtained by adhesives which are based on polyurethane, melamine formaldehyde, urea formaldehyde, phenol formaldehyde, and resorcinol formaldehyde resins. The binder should contribute 20 percent to 50 percent of the total weight of the leatherlike product.

Needle punching with or without the introduction of yarn stitches into the nonwoven base fabric enhances entanglement of the collagen fibers and synthetic fibers, and shrinking of the web by immersion in water or steaming contributes to interlocking of the fibers in a manner known in itself.

What is claimed is:

l. A leather substitute comprising:

a. A minor portion of collagen fibers having a length of at least 1 centimeter;

b. A major portion of synthetic fibers substantially longer than said collagen fibers;

c. Said fibers being homogeneously mixed while in a substantially dry state in a three-dimensional pattern, and formed into a substantially continuous web and;

d. A resinous bonding agent comprising between 20 to 50 percent by weight of said fibers adhesively bonding said fibers to each other in a nonwoven fabric structure.

2. A leather substitute as set forth in claim 1, wherein said manmade fibers are chopped staple fibers of viscose rayon, polyalkylene, polyester, polyvinyl alcohol, polyvinyl chloride, or acrylic polymer.

3. A leather substitute as set froth in claim 1, wherein said bonding agent contains a resin base a polyurethane, a polyamide, a melamine formaldehyde, a urea formaldehyde resin, a phenol formaldehyde resin, or a resorcinol formaldehyde resin.

4. A leather substitute as set forth in claim 3, wherein the amount of bonding agent is between 25 and 40 percent by weight of finished product.

5. The method of making a leather substitute which comprises the steps of a. Preparing in substantially dry form a major amount of collagen fibers having a length of at least one centimeter with a minor amount of synthetic fibers;

b. Mixing said fibers to form a homogeneous mass of intermixed and intertangled fibers c. Forming a web from the mixed fibers; and

d. Applying to said web resinous adhesive bonding agent in an amount between 20 to 50 percent by weight of said mixture for binding said fibers to each other in a nonwoven fabric structure having a three dimensional pattern.

6. The method, according to claim 5 wherein the synthetic fibers are chopped staple fibers of this viscous rayon, polyalkylene, polyester, polyvinyl alcohol, polyvinyl chloride, and acrylic polymer.

7. The method according to claim 6 wherein the amount of binding agent is between 25 and 40 percent by weight of said mixture.

8. The method according to claim 7 wherein said bonding agent is a polyurethane having approximately 20 percent nonvolatile solids having free isocyanate groups. 

2. A leather substitute as set forth in claim 1, wherein said manmade fibers are chopped staple fibers of viscose rayon, polyalkylene, polyester, polyvinyl alcohol, polyvinyl chloride, or acrylic polymer.
 3. A leather substitute as set froth in claim 1, wherein said bonding aGent contains a resin base a polyurethane, a polyamide, a melamine formaldehyde, a urea formaldehyde resin, a phenol formaldehyde resin, or a resorcinol formaldehyde resin.
 4. A leather substitute as set forth in claim 3, wherein the amount of bonding agent is between 25 and 40 percent by weight of finished product.
 5. The method of making a leather substitute which comprises the steps of a. Preparing in substantially dry form a major amount of collagen fibers having a length of at least one centimeter with a minor amount of synthetic fibers; b. Mixing said fibers to form a homogeneous mass of intermixed and intertangled fibers c. Forming a web from the mixed fibers; and d. Applying to said web resinous adhesive bonding agent in an amount between 20 to 50 percent by weight of said mixture for binding said fibers to each other in a nonwoven fabric structure having a three dimensional pattern.
 6. The method, according to claim 5 wherein the synthetic fibers are chopped staple fibers of this viscous rayon, polyalkylene, polyester, polyvinyl alcohol, polyvinyl chloride, and acrylic polymer.
 7. The method according to claim 6 wherein the amount of binding agent is between 25 and 40 percent by weight of said mixture.
 8. The method according to claim 7 wherein said bonding agent is a polyurethane having approximately 20 percent nonvolatile solids having free isocyanate groups. 